In the course of normal operations, and especially heavy duty use, of reciprocating piston apparatus, as internal combustion engines, piston pumps and the like, the cylindrical journals or piston crank pins between the crankshaft counterweight plates, and upon which the connecting rods to the pistons are mounted, experience significant wear. While sleeve or similar split bearings are normally interposed between the cylindrical journals and the surrounding connecting rod sections, as various well known sleeve bearings of Babbitt metal, bronze, and the like, nonetheless out-of-round wear can and does occur to the journals. In the case of an internal combustion engine, the stress applied on each power stroke of the piston is applied immediately and directly to the crankshaft journals. The same considerations apply in heavy duty pumping equipment wherein the stress of the journals is applied as the crankshaft is driven.
Out-of-round journal wear causes vibration and excess stress in the reciprocating piston apparatus, which can induce eventual or even immediate failure of the apparatus, with major loss of equipment service and operation time as well as large repair costs. While such large costs may be accommodated in the case of large industrial fixed-in-place engines or motors in a generating or pumping plant, for example, the expense is relatively staggering and impractical in the case of relatively lower-cost equipment, as consumer automobiles or smaller industrial equipment, as backhoes, and the like.
In effecting journal repair in an automobile, for example, it is presently necessary, and common practice, to physically remove the engine from the vehicle chassis, and then essentially to disassemble the engine in order to gain access to, remove, and effect regrinding and truing of worn journal connectors. This, as is evident, is a laborious and time-consuming project. Thus, after the engine is physically removed from the automobile chassis after freeing all connections thereto, thereafter, briefly stated, the engine must be disassembled, at a minimum, by removal of the crankcase, front and rear crankshaft bearings and covers, removal of the crankshaft and all connecting rods and pistons. Thence, the lower connecting rod cap sections about the journals must be removed to detach the connecting rods and pistons, thereby freeing the crankshaft as a unit for separate handling to recondition the connecting rod journals as necessary. Not only is there the aforesaid burden of disassembling the engine, but also, the crankshaft must thereafter be shipped or transported to a suitable machine shop to correct and true the journals. After the journals have been ground and retrued to desired cylindrical form, the corrected crankshaft must be returned, and thence reinstalled during full re-assembly of the engine or other reciprocating piston apparatus.
The downtime of the engine for all of this effort is necessarily great, and the costs often in the thousands of dollars, which is an exceeding burden for an automobile owner as well as for small business enterprises. The downtime and costs are much greater in the case of larger reciprocating piston engines as employed in industrial vehicles such as fork lift trucks, earthmoving equipment, front end loaders, backhoes, among many other such equipment, wherein is necessary to remove the engine from the chassis of the vehicle.
Prior efforts have been made to reduce this significant economic and operating burden in the correction of crankshaft journals. Such techniques are referred to as "on-site" journal correctors or reconditioning devices. See, for example, U.S. Pat. No. 4,609,312 to Sverdlin, or the article by the engineering firm Nicol & Andrew entitled On-Site Machining Equipment, among other generally similar techniques.
In such devices, it is desired that the large crankshafts not be transported at great cost, but repaired at the site, which is usually a fixed engine or motor location. In so doing, while costs of shipment are avoided, still all connecting rods, bearings, and related shaft components must be removed, and relatively complex abrading equipment is mounted about the journal. In operation, such abrading equipment is physically rotated about the journal with the axis of the journal as the center of rotation while the crankshaft is stationary. This, while physical and time-consuming transport of the crankshaft is avoided, the nonetheless difficult burden of extensive shutdown, disassembly, and reassembly is required.